Floating mirrors

We discuss a new technology that promises large, inexpensive mirrors. We ar gue that it should be possible to tilt a rotating viscous liquid by perhaps as much as a few tens of degrees. The tilted liquid parabolic surface is u sed as the support for a thin reflecting metallic film. It may also be poss ible to use it to support an ultrathin glass mirror. We demonstrate two cri tical steps: that a viscous liquid mirror can be tilted and that an optical -quality metallic film can be deposited on a liquid. The advent of astronom ically useful tilted floating-mirror telescopes is contingent on the develo pment of high-viscosity, high-reflectivity liquids. It is a good omen that we already have identified two classes of such liquids; however, there rema in technical challenges to overcome before such liquids can be used in viab le telescopes.